Hi Tim =)
I'm not sure I understand what you're aiming for. If you attach a link to/photo of another map, or more, that illustrates the style you are hoping to accomplish, it'll be easier for people to give advice.
EDIT: Oh, and, there's also this free pdf book thing, about creating fantasy maps using Earth rules... It's called 'A Magical Society Guide to Mapping'. I found it useful. There are multiple places you can download it from; just do a Google search. You'll find it.
But as a quick pointer, I'd say that newer continental breaks or collisions would be sharper, older ones would have time to erode and soften.